You could leave your containers outside if you scatter sharp stones on top of the compost . . . I do this with all my pots, and the squirrels (here daily) leave them alone.

or cover the top with wire netting buried below the gravel topping.
If you bring them into the greenhouse then yes you will have to water them,sparingly over winter. They need to be moist, but not drowned. They will probably flower earlier too.

Most Spring bulbs require a cold treatment in order to bloom properly. There is a way to force them. Here is a website that will help you.

http://www.gardeningknowhow.com/ornamental/bulbs/bgen/chilling-flowering-bulbs.htm

Thank you all for your replies and advice.

Helen